Abstract: A novel prophylactic/remedy for immunopathy is provided which is not neutralized by a neutralizing antibody to Staphylococcal enterotoxin B (SEB), known as one of superantigens, and may effectively act as a superantigen. A modified SEB having a reduced reactivity with a neutralizing antibody to SEB (anti-SEB antibody) and a prophylactic/remedy for immunopathy comprising as an active ingredient said modified SEB. The modified SEB of the present invention may be prepared with the evolutionary molecular engineering technique by introducing amino acid substitution in the amino acid sequence of SEB, especially at an epitope recognition site of the anti-SEB antibody in the amino acid sequence of SEB.